Many individuals are dissatisfied with their current tooth color. Thus, there is a desire for whiter teeth and one means to achieve whiter teeth is the use of tooth whitening products.
It is known in the literature that the visual perception of a white substance can be altered through the deposition of an optical brightener, blue pigment or blue dye, especially one for which the hue angle (in the CIELAB scale) of the reflected or emitted light is between 200 to 320 degrees. This effect is commonly used in laundry detergent products to make white clothes appear “whiter” to the human eye. The same concept has been applied to tooth whitening as well. The natural off-white or yellow color of teeth can be made to appear whiter through the deposition of a blue substance onto teeth. Using pigments with a deposition aid, i.e., high molecular weight Gantrez® type polymers (copolymers of maleic anhydride and with methyl vinylether) in toothpaste to make teeth look whiter is disclosed in EP 1935395B1.
Dentifrice formulations comprising peroxide are known and useful for cleaning and whitening teeth. The peroxide can bleach the teeth, remove stains, and kill cariogenic bacteria. However, peroxide compounds are highly reactive, and consequently difficult to formulate. Moreover, hydrogen peroxide can spontaneously decompose to form oxygen gas (O2) and water, so that on storage, the dentifrice containers may bloat, burst or leak, and the remaining formulation will not have enough peroxide remaining to clean and whiten teeth effectively. Some dentifrices initially comprise very high levels of peroxide, which decomposes over time, so that the exact amount of peroxide delivered on application is variable and largely depends on how long and under what conditions the dentifrice has been stored.
Due to the color bleaching property of hydrogen peroxide, products containing hydrogen peroxide are usually clear or off white.
There is thus a need for improved color stable whitening oral compositions which effectively stabilizes both hydrogen peroxide and pigment that are suitable for everyday consumer use.